A reclosable zipper-equipped bag having at an opening thereof an engageable belt-like zipper tape a pair of mating male and female members has been utilized as a packaging application for packaging a variety of goods such as food, drugs and other medical products, miscellaneous goods and the like. In a widely employed manufacturing method of the zipper-equipped bag whose opening is reclosable, a zipper tape is manufactured in advance before being heat-sealed on base films that form a bag body.
Before a user opens and recloses the zipper tape of the zipper-equipped bag, the zipper-equipped bag is in a closed state by a heat-seal at a periphery of the bag body (side seal) and a heat-seal near an opening end of the bag (top seal). When the zipper tape is opened to take out a product in the bag body, a portion near the opening end of the bag body including top seal has conventionally been cut and removed to allow the zipper tape to be opened so that the product can be taken out.
More often than not, the zipper-equipped bag having such an arrangement fails to achieve air-tightness or water-tightness. For example, when the zipper-equipped bag encapsulating a fluid product is transported, the product leaks through a tiny gap in the engaged portions of the zipper tape or through a boundary between a collapsed portion of the side seal and the engaged portions of the zipper tape toward the top seal.
Various attempts have been made to provide the zipper-equipped bag with air-tightness or water-tightness. For example, a zipper-equipped bag in which mating fastener tapes (zipper tapes) are bonded with each other at portions thereof adjacent to the product in an easily peelable manner via a hot-melt adhesive or the like is provided (e.g. see Patent Document 1).
Another package bag has been disclosed in, for example, Patent Document 2. A base portion of the zipper tape is wider than the other base portion. A sealant is provided on a portion of the first (wider) base portion adjacent to the engagement portion. When the bag is opened, a first flange on which the sealant is provided is separated from a second flange on which an engagement member is provided.
Still another package bag has been disclosed in, for example, Patent Document 3. The bag has a reclosable zipper tape. Prior to use, a dividing wall provided near a lower end of the zipper tape prevents a fluid from travelling toward the zipper tape. Upon use, the dividing wall can be easily peeled with the same force that opens and closes the zipper.    Patent Document 1: JP-A-2004-168420 (claim 1, FIG. 2)    Patent Document 2: International Publication 2004/050487 Pamphlet    Patent Document 3: JP-A-2005-40630